One example of an image forming apparatus is an inkjet recording apparatus. An inkjet recording apparatus records information (prints characters, prints photographs, forms images, and so on) by spraying ink from recording heads onto a medium (hereafter called a paper sheet, which is not limited to a sheet of paper but also includes an OHP sheet, a recording medium, recording paper, and the like).
In general, such an image forming apparatus is equipped with replaceable ink-containing units called ink cartridges or ink tanks for supplying ink to the recording heads, and is configured to display a warning when an ink-containing unit is low in ink or out of ink.
[Patent document 1] Japanese Patent Application Publication No. 2002-370382
A host computer for managing the amounts of remaining color materials in an image forming apparatus is disclosed in patent document 1.The host computer includes a remaining-ink-amount calculation unit for calculating the amount of remaining ink by subtracting the amount of consumed ink in an ink tank of a recording head from the amount of ink initially contained in the ink tank, a remaining-ink-amount information retaining unit for retaining remaining-ink-amount information on the amount of remaining ink for each recording head calculated by the remaining-ink-amount calculation unit, and a remaining-ink-amount information output unit for outputting for users the remaining-ink-amount information retained in the remaining-ink-amount information retaining unit.
[Patent document 2] Japanese Patent Application Publication No. 2005-22146
A remaining-ink-amount detecting apparatus is disclosed in patent document 2. The remaining-ink-amount detecting apparatus is implemented in an inkjet recording apparatus having a carrier for holding ink cartridges and detects the amounts of remaining ink in the ink cartridges in the carrier by using detecting elements on ink cartridges.
[Patent document 3] Japanese Patent Application Publication No. 9-11490
An inkjet recording apparatus is disclosed in patent document 3.The inkjet recording apparatus includes a counting unit for counting the number of dots of print data loaded into a print buffer which can at least contain an amount of print data for one scan, a calculating unit for calculating the amount of ink needed to print the print data (A) based on the counted value, a calculating unit for calculating the amount of ink consumed in print head cleaning (B), a calculating unit for calculating the amount of remaining ink in an ink-tank based on the amounts of ink (A) and (B), a display unit for displaying a message regarding the amount of remaining ink, and a non-volatile memory apparatus for storing the information on the amount of remaining ink.
[Patent document 4] Japanese Patent Application Publication No. 10-175312
A remaining-ink-amount detecting apparatus is disclosed in patent document 4.The remaining-ink-amount detecting apparatus detects the amount of remaining ink based on the liquid level of ink in an ink tank and reports, via a network, remaining-ink-amount information which is represented by the percentage of the amount of remaining ink in proportion to the amount of ink when the ink tank is full.
[Patent document 5] Japanese Patent Application Publication No. 2003-107970
A printer controller is disclosed in patent document 5.The printer controller includes a pixel counting unit for counting the number of pixels actually needed to print an image data on recording paper by using toner or ink, a consumed amount storing unit for storing the cumulative amount of consumed toner/ink which has been used so far to print image data, a processing unit for updating the value of the cumulative amount of consumed toner/ink in the consumed amount storing unit by adding the number of pixels counted by the pixel counting unit and the cumulative amount of consumed toner/ink in the consumed amount storing unit, and a remaining amount detecting unit for calculating the amount of remaining toner/ink based on the cumulative amount of consumed toner/ink in the consumed amount storing unit and the amount of toner/ink initially provided.
As described above, in conventional image forming apparatuses, the amount of remaining color material in a tank or a cartridge is used to report a situation where a tank is low in color material or out of color material, to report the percentage of the amount of remaining color material, or to report the actual amount of remaining color material.
However, with the methods of detecting the amounts of remaining color materials in such conventional image forming apparatuses, a user can know only the timing for replacing a color material tank/cartridge and not know how many pages of a document can be printed with the remaining color materials beforehand.